c c c ========================================================= subroutine rp1(maxmx,meqn,mwaves,mbc,mx,ql,qr,auxl,auxr, & wave,s,amdq,apdq) c ========================================================= c c # solve Riemann problems for the 1D Burgers' equation. c # On input, ql contains the state vector at the left edge of each cell c # qr contains the state vector at the right edge of each cell c # On output, wave contains the waves, c # s the speeds, c # amdq the left-going flux difference A^- \Delta q c # apdq the right-going flux difference A^+ \Delta q c c # Note that the i'th Riemann problem has left state qr(i-1,:) c # and right state ql(i,:) c # From the basic clawpack routine step1, rp is called with ql = qr = q. c c implicit double precision (a-h,o-z) dimension ql(1-mbc:maxmx+mbc, meqn) dimension qr(1-mbc:maxmx+mbc, meqn) dimension s(1-mbc:maxmx+mbc, mwaves) dimension wave(1-mbc:maxmx+mbc, meqn, mwaves) dimension amdq(1-mbc:maxmx+mbc, meqn) dimension apdq(1-mbc:maxmx+mbc, meqn) logical efix c c efix = .true. !# Compute correct flux for transonic rarefactions c do 30 i=2-mbc,mx+mbc c c # Compute the wave and speed c wave(i,1,1) = ql(i,1) - qr(i-1,1) s(i,1) = 0.5d0 * (qr(i-1,1) + ql(i,1)) c c c # compute left-going and right-going flux differences: c ------------------------------------------------------ c amdq(i,1) = dmin1(s(i,1), 0.d0) * wave(i,1,1) apdq(i,1) = dmax1(s(i,1), 0.d0) * wave(i,1,1) c if (efix) then c # entropy fix for transonic rarefactions: if (qr(i-1,1).lt.0.d0 .and. ql(i,1).gt.0.d0) then amdq(i,1) = - 0.5d0 * qr(i-1,1)**2 apdq(i,1) = 0.5d0 * ql(i,1)**2 endif endif 30 continue c return end